In this March 7, 2016, file photo, Denver Broncos quarterback Peyton Manning speaks during his retirement announcement at the teams headquarters in Englewood, Colo. The NFL says it found no credible evidence that Peyton Manning was provided with HGH or other prohibited substances as alleged in a documentary by Al-Jazeera America last fall.

The NFL on Monday dismissed accusations that Peyton Manning had used banned substances seven months after a news report suggested that the star quarterback had taken human growth hormone.

The allegations made in December in a documentary broadcast by Al-Jazeera sent shock waves through the NFL, which was already embroiled in an acrimonious dispute with Tom Brady, another of its top players.

Manning, though, was perhaps the league’s biggest household name, and the accusations could have tarnished his 18-year career just as he was edging toward retirement.

The league’s statement that it had “found no credible evidence” that Manning received or took prohibited substances closed the book on the awkward scandal, and came just two weeks after Brady ended his fight to overturn the four-game suspension he received for his role in an alleged scheme to deflate balls used in the AFC championship game in 2015.

The league, however, said that it would continue to investigate other allegations against other players made in the Al-Jazeera report, which included suggestions that many big stars in Major League Baseball and the NFL had been taking designer steroids and other banned performance-enhancing drugs.

One specialist, Charles Sly, a pharmacist at the center of the Al-Jazeera report, said that the Guyer Institute, an anti-aging clinic in Indianapolis where he had worked, had sent shipments of human growth hormone to Manning’s wife, Ashley. Sly later recanted his accusation.

Manning vigorously denied the report, saying it was “complete garbage” and “totally made up.”

Sly also linked James Harrison, Clay Matthews and other NFL players, as well as MLB players Ryan Howard and Ryan Zimmerman, to PED. All deny the charges, and Howard and Zimmerman sued Al-Jazeera for libel.

Another MLB player, Taylor Teagarden, was seen on camera talking about taking PED. The MLB suspended him for 80 games.

Though the league has cleared Manning, his case remains the most controversial. The report was released in the midst of what turned out to be Manning’s final season in the league, and it is unclear whether the allegations played any role in his decision to retire. It is also unclear whether Manning was under any obligation to cooperate with an investigation after he left the league, and whether the league had any means of penalizing him had they found that he had taken banned substances.

The league also appeared reluctant to work on a broader investigation of allegations made in the documentary. The NFL denied news reports that it had initially declined to work with the MLB and the U.S. Anti-Doping Agency.

The accusations against Manning were also particularly hazy. The Al-Jazeera report did not specify, for example, how much human growth hormone Sly claimed to have sent to Manning’s wife when he worked at the Guyer Institute or over what period.

Manning admitted that he was treated at the clinic in 2011 while recovering from a neck injury, but said that the treatment was given with the full knowledge of the team doctor and did not involve banned substances. He said he had used a hyperbaric chamber there to speed his recovery. Manning said his wife’s medical status was private.

“It never happened,” Manning said the day the documentary was released. “Never. I really can’t believe somebody would put something like this on the air. Whoever said this is making stuff up.”

To confuse matters, Sly recanted his allegations in a video, saying, “There is no truth to any statement of mine that Al-Jazeera plans to air.”

A Washington Post article suggested that Sly might have made that video under duress. The paper said that private investigators hired by Manning had visited Sly’s parents’ house twice and questioned him before the homemade video confession.

Dr. Dale Guyer, founder of the institute, said of the report, “I find it extremely disturbing that the source of Al-Jazeera’s story, a former unpaid intern named Charles Sly, would violate the privacy of Mrs. Manning’s medical records.” He called the allegations “simply not true.”

Nearly all of the athletes Sly named, including Howard and Zimmerman, are clients of Jason Riley, a fitness trainer based in Sarasota, Florida. Riley and Sly are former business partners.

Sly’s comments were made to Liam Collins, once a top hurdler for Britain, who had posed as an athlete in search of performance-enhancing drugs. He taped a number of conversations surreptitiously.

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